The field of this invention relates to energy absorption apparatuses and more particularly to a spring damper which employs the use of a compressible solid material with the device of this invention to have a first damping rate for low energy loads and a second damping rate for high energy loads.
The energy absorption unit of this invention has been found to be especially useful in automobiles to be located between the body of the vehicle and the bumper. However, it is considered to be within the scope of this invention to employ the apparatus of this invention in any other environment as it is well known that spring damping apparatuses are used in numerous fields.
Automobiles have always employed some means to protect the body of the vehicle from slight bumps. Such means have normally been referred to as bumpers which are located in the front and rear portions of the vehicle. The bumpers are formed normally of a rigid piece of material, such as steel, which is secured to the vehicle. Upon the vehicle being struck by another vehicle, or if the vehicle strikes a fixed object, the material of construction of the bumper normally fails upon incurring even a slight, small impact force. Additionally, such bumpers normally directly transmit the force into the vehicle itself. Such transmission of force is undesirable since it causes further damage to the vehicle and frequently causes injury to the vehicle occupants.
Heretofore, bumpers have been developed for vehicles which absorb impact forces and attempt to minimize the transmission of a significant amount of the impact force into the vehicle structure. The energy absorption units which are employed upon these bumpers are designed to absorb a low energy impact force, such as up to 10 miles per hour, with the vehicle not incurring any damage. However, upon the vehicle being struck with a large impact force, the energy absorption units of the prior art will fail immediately, thereby not absorbing any energy with the result that the effect of the energy absorption unit is completely negated. It would be desirable to design an energy absorption unit which could absorb impact energies at a normal closing velocity of say 10 miles per hour without causing any damage to the vehicle and it would also be desirable that if the vehicle is subjected to a very high velocity such as 50 miles per hour, that the unit would function and absorb some of the impact energy. It is considered feasible that a vehicle would be designed, if driven into a solid barrier at a very high velocity, a finite portion of the impact energy could be absorbed by the energy absorption units, and the remaining impact energy absorbed by the vehicle collapsing in a particular manner, with the result that the impact energy transferred into the passenger compartment is minimized.